Fitness cost of self-fertilization in plants

Published online 10 June 2013

Aisha El-Awady

The evolution of flowering plants that require another plant to reproduce, or cross-fertilize, to ones that can self-fertilize is a common change. Scientists, however, are yet to fully understand the genetics involved.

To better understand how plants can reproduce by themselves, an international team of researchers, led by Tanja Slotte from Uppsala University, and including Khaled Hazzouri from New York University Abu Dhabi, UAE, sequenced the genome of Capsella rubella, a self-fertilizing plant that separated from its cross-fertilizing ancestor Capsella grandiflora within the past 200,000. They compared it to genomes of two species of Arabidopsis, publishing their findings in Nature Genetics1.

Comparing RNA expression and polymorphism patterns between the two Capsella species, they found that C. rubella had a decreased ability to eliminate harmful mutations than C. grandiflora and exhibited a change in the expression of reproduction-related genes similar to that seen in Arabidopsis, which became self-fertilizing plants about 1 million years ago. This was not accompanied by a change in the abundance or activity of transposable elements — genetic material capable of inserting copies of itself into other DNA sites.

"The results underscore the long-term advantages of outcrossing, which is the practice of mating between individuals, that maintains genetic variation and eliminates harmful mutations," says Stephen Wright from the University of Toronto, one of the lead authors on the study. "Selfing is a good short-term strategy but over long timescales may lead to extinction."